In radioactively-ladened shielded cells such as large-area cells in a nuclear reprocessing facility, maintenance of the process components and the conduits interconnecting the same must be carried out by remote manipulation. If it is necessary during maintenance operations to remove a segment of a conduit from a vertical conduit and weld a fresh segment into place, care must be taken to ensure that the chips which are formed during the severing operation and/or the preparation of the weld seam do not remain in the conduit and thus contaminate the liquid medium therein.
Removing the cutting waste from the upper end of the conduit does not give rise to any problems. However, removing such material from the lower end of the conduit causes difficulties. The chips accumulate on the frost plug which is formed in the conduit and which was produced underneath the lower saw cut in the lower end portion of the conduit by means of a suitable freezing apparatus. The chips penetrate into the frozen plug and can only be partially removed if at all.